1. Field of the Invention
The present invention relates to a control valve for a constantly pilot flaming type vessel gas water heater in which the temperature of hot water in a reservoir can automatically be controlled to a desired level.
2. Description of the Related Art
Such a conventional control valve for a vessel gas water heater has, for example, a main burner governor valve unit MGVxe2x80x2 provided across a main gas passage and a pilot burner governor valve unit PGVxe2x80x2 provided across a pilot gas passage as shown in FIG. 3. The main burner governor valve unit MGVxe2x80x2 is arranged in that, when not in use, its gas valve V4xe2x80x2 is lifted and closed by the action of a taper cam 2axe2x80x2, which is mounted to the distal end of an ignition operating shaft 2xe2x80x2 linked integral with an ignition knob 1xe2x80x2, pressing via a link lever 30xe2x80x2 together with a diaphragm 15xe2x80x2 as resisting against the yielding force of an adjusting spring 16xe2x80x2. The pilot burner governor valve unit PGVxe2x80x2 comprises a diaphragm 15xe2x80x3, a gas valve V4xe2x80x3, and an adjusting spring 16xe2x80x3.
For starting the ignition, the ignition knob 1xe2x80x2 is turned from the xe2x80x9cstopxe2x80x9d position to the xe2x80x9cpilotxe2x80x9d position and then depressed by one stroke, hence activating the ignition operating shaft 2xe2x80x2 to push and open the magnetic valve V1xe2x80x2 of a safety solenoid valve unit MVxe2x80x2. This allows the gas to run from a gas inlet 5axe2x80x2 via the pilot burner governor valve unit PGVxe2x80x2 mounted across the gas passage to the pilot burner PBxe2x80x2. As the gas is ignited by a match or lighter, a pilot flame cxe2x80x2 is produced thus maintaining the magnetic valve V1xe2x80x2 open. At the time, the gas valve V4xe2x80x2 of the main burner governor valve unit MGVxe2x80x2 remains closed. Then, the ignition knob 1xe2x80x2 is released from being pressed and turned further from the xe2x80x9cpilotxe2x80x9d position to the xe2x80x9copenxe2x80x9d position. As a result, the lifting and closing of the gas valve V4xe2x80x2 of the main burner governor valve unit MGVxe2x80x2 by the taper cam 2axe2x80x2 of the ignition operating shaft 2xe2x80x2 is canceled. Once the gas valve V4xe2x80x2 is freed and open, it then acts as a governor valve in cooperation with the diaphragm 15xe2x80x2.
Since the magnetic valve V1xe2x80x2 serves as a plunger valve, it requires an extra mechanism for being forced to the closing position, which is implemented by a switch Sxe2x80x2 provided in an electromagnetic circuit to disconnect the safety solenoid valve unit MVxe2x80x2 from the power supply. Only when the ignition knob 1xe2x80x2 is turned to the xe2x80x9cstopxe2x80x9d position, the switch Sxe2x80x2 is switched off to close the magnetic valve V1xe2x80x2.
When the temperature of hot water in a reservoir Axe2x80x2 is lower than a desired level, the action of a sensor rod Bxe2x80x2 drives a snap lever 23xe2x80x2 to move a snap disk 25xe2x80x2 to the opposite position, thus opening a snap valve V5xe2x80x2 to supply a flow of gas to the main burner. The gas is then ignited by the pilot flame cxe2x80x2 hence increasing the temperature of the hot water in the reservoir Axe2x80x2 to the desired level. As the hot water in the reservoir Axe2x80x2 reaches the desired temperature, it is sensed by the sensor rod Bxe2x80x2 which in turn moves back the snap disk 25xe2x80x2 to the original position (at the standby state) Simultaneously, the snap valve V5xe2x80x2 is closed to extinguish the flame of the main burner providing the standby state. Denoted by Fxe2x80x2 is a thermal fuse provided in the electromagnetic circuit and 28xe2x80x2 is a temperature setting screw which supports the proximal end of the snap lever 23xe2x80x2. Also shown is a pilot filter 31xe2x80x2.
However, the conventional control valve described above includes the main burner governor valve unit MGVxe2x80x2 and the pilot burner governor valve unit PGVxe2x80x2, incorporating a two-governor system. Therefore, its structure will be complicated and its overall size will hardly be minimized, hence increasing the production cost.
Also, the electromagnetic circuit contains the electric switch Sxe2x80x2 and the thermal fuse Fxe2x80x2, permitting the resistance to increase with time. As the resistance increases in the electromagnetic circuit, the current will proportionally be declined.
It is thus an object of the present invention to provide a control valve for a vessel gas water heater having a single governor provided for controlling the flow of gas for a wider range from pilot supply to main supply thus to eliminate the foregoing problems as of the prior art.
As defined in claim 1 of the present invention for solving the above problems, a control valve for a vessel gas water heater is provided having an ignition knob pressed and turned for opening the magnetic valve and igniting the pilot burner, the magnetic valve maintained open by the electromotive force of a thermocouple heated with a pilot flame, and then, the ignition knob released from being pressed and turned further for opening the plunger valve to enable the supply of gas to the main burner, and having a sensor rod for contracting and expanding depending on the temperature of hot water in a reservoir to open and close the snap valve and thus proceed and cancel the combustion in the main burner for automatically controlling the temperature of the hot water in the reservoir to a desired level, characterized by a single governor valve unit arranged in that the positional relationship between its valve and valve seat is correctly maintained to have a wide range of the flow of gas from a pilot supply to a main supply, thus enabling stable control over both the flow of gas to the main burner and the flow of gas to the pilot burner.
As defined in claim 2 of the present invention, the control valve for a vessel gas water heater according to claim 1 may be modified in which the governor valve is also arranged in that the interfacial accuracy between the valve and the valve seat is improved and the valve is prevented from tilting.
As defined in claim 3 of the present invention, the control valve for a vessel gas water heater according to any of claims 1 and 2 may be modified in which the valve seat for the valve is increased in the seating tightness using a rubber molding and fine polishing.
As defined in claim 4 of the present invention, the control valve for a vessel gas water heater according to any of claims 1 and 2 may be modified in which the valve is prevented from tilting by a guide pin freely fitted in a shaft of the valve.
As defined in claim 5 of the present invention, the control valve for a vessel gas water heater according to claim 1 may be modified in which the pilot burner is a constantly flaming type pilot burner designed for also heating a thermocouple.
The control valve for a vessel gas water heater defined in claim 1 of the present invention, which is arranged in that the ignition knob is pressed and turned for opening the magnetic valve and igniting the pilot burner, the magnetic valve is maintained open by the electromotive force of the thermocouple heated with the pilot flame, and then the ignition knob is released from being pressed, and turned further for opening the plunger valve to enable the supply of gas to the main burner and thus set the standby state while the sensor rod is provided for contracting and expanding depending on the temperature of hot water in the reservoir to open and close the snap valve and thus proceed and cancel the combustion in the main burner for automatically controlling the temperature of the hot water in the reservoir to a desired level, is characterized by the single governor valve unit arranged in that the positional relationship between its valve and valve seat is correctly maintained so that the supply of the gas is constantly flown corresponding to the requirement for the pilot supply and the main supply which ranges widely from the pilot supply to the main supply. As a result, the control valve of the present invention will be simplified in the construction and reduced in the production cost as compared with any conventional two-governor type.
The control valve for a vessel gas water heater defined in claim 2 of the present invention has the governor valve arranged in that the interfacial accuracy between the valve and the valve seat is improved and the valve is prevented from tilting, hence allowing the single governor valve unit to control throughout a wider range of the flow of the gas from the pilot supply to the main supply. Accordingly, the control valve defined in claim 1 can be implemented with much ease.
The control valves for a vessel gas water heater defined in claims 3 and 4 are arranged in which the valve seat for the valve is increased in the seating tightness using the rubber molding and the fine polishing and in which the valve is prevented from tilting by the guide pin freely fitted in the shaft of the valve, hence allowing the positional relationship between the valve and the valve seat to be correctly maintained. Accordingly, the control valve defined in claim 1 or 2 can be implemented with much ease.
The control valve for a vessel gas water heater defined in claim 5 is modified in which the pilot burner is a constantly flaming type pilot burner designed for also heating the thermocouple, allowing the magnetic valve to be closed by extinguishing the pilot flame. Accordingly, such a disadvantage that the electromagnetic force is declined due to the increase with time of the resistance in the magnetic circuit equipped with an electric switch can be eliminated thus improving the operational reliability.